1. Field of the Invention
The present invention is related to a dipole antenna array, and especially to an antenna array of which dipole antennas are taken as a basis to form an antenna array, thereby the width of frequency band and gain can be increased to provide the functions of dual frequency or multiple frequency antennas.
2. Description of the Prior Art
In the primary stage of marketing of mobile phones, exposed helical coils structures are used as the main components of antennas. The coil antennas widely used nowadays are generally divided into two main typesxe2x80x94contractible and fixed types. No matter which kind of structure is used, an antenna normally has a specific length protruding out of the top surface of the body of a mobile phone. Therefore, various microstrip antennas have been developed, such microstrip antennas are characterized by planeness, concealment and non occupying too much volume.
The microstrip antennas disclosed in the U.S. Pat Nos. 3,921,177 and 3,810,183 are generally composed of round or rectangular metallic sheets, there are dielectrics filled between the antennas and the ground; however, such microstrip antennas only allow narrower widths of frequency. Taiwan patent no. 81,108,896 (with a U.S. patent application filing number of 07/798700) provides a microstrip antenna being reduced by size but with a broadband. However, it has the defect of providing a helical antenna component on a grounding floor separating therefrom, and a dielectric with a specific thickness and loading material are provided therebetween, the size of the antenna is still hard to further be reduced though.
Among modern planar inverted F-antennas (PIFA), dual-frequency antennas (IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL 45, NO.10, OCTOBER 1997) are of an ideal type of miniaturized microstrip antenna, however, by the fact that:             Electrical      ⁢              xe2x80x83            ⁢      volume      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      an      ⁢              xe2x80x83            ⁢      antenna              frequency      ⁢              xe2x80x83            ⁢      band      xc3x97      gain      xc3x97      efficiency        =      a    ⁢          xe2x80x83        ⁢    constant  
So long as the antenna is made planar and miniaturized, its bandwidth and efficiency of radiation will be reduced and will be necessary to be improved.
The object of the present invention is to provide a dipole antenna array that can solve the problem of insufficiency of the widths of frequency bands and radiating efficiencies of microstrip antennas, and can effectively suit various portable communication equipments as dual frequency or multiple frequency antennas.
To get the above stated object, the present invention provides a dipole antenna array by connecting a plurality of dipole antennas, one end of the dipole antenna array has an open stub and a balancing circuit to adjust the width of frequency band, impedance and gain of the antenna array.
In a further embodiment, each dipole antenna is added on the two ends thereof with antenna loading devices such as a plurality of mini-aperture antennas.
In an ideal embodiment, the above stated dipole antenna array can have an option to add a reflector to increase its gain.
The present invention will be apparent in its novelty and other characteristics after reading the detailed description of the preferred embodiment thereof in reference to the accompanying drawings. Wherein: